In the rat, a normal physiological consequence of the LH-secretion during proestrus is the induction of the enzyme, ornithine decarboxylase, in the ovary. This enzyme synthesizes putrescine which is the precursor of the polyamines, spermidine and spermine, thus, suggesting the involvement of polyamines in the reproductive process. A study of the nature of the induction of ornithine decarboxylase by the hormone LH, the relationship of this enzyme to another enzyme, S- adenosylmethionine decarboxylase, which synthesizes the proplyamine moeity of the polyamines, afd the consequences of the inhibition of one or both of these enzyme systems relative to ovulation will be undertaken. A detailed study of putrescine metabolism has revealed a disparity between its synthesis rate and that of spermidine and spermine in the rat ovary and placenta. The high rate of putrescine synthesis by induced ornithine decarboxylase in the absence of a concomitant significant increase in spermidine or sperming biosynthesis suggests a primary physiological role for putrescine itself. A correlation between changes in ornithine decarboxylase activity with putrescine content and RNA synthesis will be sought.